One of the greatest problems facing space programs has been, and continues to be, the cost of putting payloads into space. That cost is a direct consequence of the launch system weight required to get a given payload out of the earth's gravity well. With current technology, that equates to about $25,000 or more for every 1 pound of payload just to get to orbit. Lunar or Mars missions will cost much more.
In an effort to reduce this cost ratio, space agencies have implemented payload-to-orbit cost reduction initiatives. These initiatives have included several new technologies and demonstrator programs. The objective was to bring the payload cost down to $1000/pound or less. However, this objective has proven elusive. For example, testing of lightweight composite tanks indicated that they may not be able to meet launch stresses. The conclusion is that the composite strength required for large lightweight tanks is not achievable with present day materials. But, these types of tanks will be crucial for reducing lift cost significantly and achieving reasonable Lunar and Mars mission cost.
Also, a big problem facing the automotive industry in its efforts to convert to hydrogen fuel is how to store large amounts of hydrogen on the vehicles. A good solution is to compress the hydrogen to very high pressures, over 10,000 psi. But, the safety and reliability of present day composite fuel tanks at these high pressures is questionable.
There was a new material breakthrough discovery made in 1991 by Sumio Iijima of NEC Laboratory in Tsukuba Japan, on a new type of carbon structure called a carbon nanotube (CNT). These tubes actually are abundant in nature and have been around forever. The outstanding properties of CNT were not realized until Iijima determined that they were tubular graphene pieces. The carbon bond of graphene (sp2) is stronger than that of diamond (sp3). CNT can now be readily made in laboratories. A high energy arc through a carbon rod produces carbon soot, which contains CNT. The significance of the tubular shape is that the graphene sheet is rolled into a continuous crystal structure giving it a tensile strength stronger than any other known material CNT can be over 100 times stronger than steel, with a strength to weight ratio 30 times greater then Kevlar. Suddenly, hypothetical structures (like a space elevator) have become theoretically possible.
Since the discovery of the properties of CNT, there has been an enormous amount of research on CNT and efforts to commercialize it. However, a big drawback to commercial applications is that the tubes can only be made several micrometers long at best. This short length eliminates the possibility of spinning or weaving them into optimal fibers or wires. If CNT wire could be made, it could be woven into composite materials for composite tanks and other lightweight structures for space applications. The high tensile strength of CNT wire will allow much greater burst pressure in composite tanks, enabling them to withstand the launch stresses. This same technology can be used to produce the needed very high pressure hydrogen fuel tanks for the automobile industry. Also, CNT wire in struts, beams, and panels will allow lighter and more fuel efficient transportation vehicles like cars, trucks, and planes; will enhance the building industry allowing longer bridges and taller buildings; and will greatly enhance military armored vehicles and body armor capabilities.
Presently, CNT made in a controlled manner in industry and laboratories is grown. One method now used to grow CNT is to place catalyst dots on a baseplate or substrate. Growth is from the bottom up, as the catalyst adds carbon atoms to the tube. One study showed that the catalyst clusters actually oscillate from dome to rod shapes and back (shape-shift) as the tubes grow. Historically, the tube's growth stops after it becomes a few micrometers long due to the tube's mass exceeding the catalyst capability.
What is needed then is to produce CNT in continuous extruded wire form, and to weave these wires into fabrics for incorporation into composite materials, enabling very high strength lightweight fuel tanks, structural members, and armor.